1994 Fiscal Year Final Research Report Summary
DETECTION OF LOW LEVEL ALPHA EMITTING MATERIAL USING A BRAGG CURVE COUNTER
| Project/Area Number |
05640360
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | NAGASAKI INSTITUTE OF APPLIED SCIENCE |
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Principal Investigator |
KIMURA Kikuo NAGASAKI INSTITUTE ENGINEERING,PROFESSOR OF APPLIED SCIENCE, 工学部, 教授 (60108636)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Bragg curve counter / Multi-wire proportional counter / Alpha radioactive material / Environmental radioactivity |
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| Research Abstract |
Background Counting
A Bragg curve counter using a multi-wire proportional chamber was constructed and the background level of this counter was measured.A raw counting rate was about one per minute.Since all the counts were recorded as waveform data of output signals, it was determined whether each signal was due to an alpha particle or not and what angle did the particle entered into the counter by analyzing waveform data.As a result of this, alpha particles emitted around the place where a test sample will be located was found to be 4 counts per hour.This remains as a final background which cannot be rejected even by applying wavefrom cut.Since this background looked to originate from alpha emitters contained in the counter material, the material was replaced by a less alpha emitting one.Then the final background was reduced to 0.4 count per hour.
Measurement using an environmental sample
Alpha particle counting form a lead sheet used as a painting tube was made by the Bragg curve counter.The events which looked to be alpha particles emitted from the place near the lead sample were selected from the raw data.It was found that the number of events when the lead sample was placed were about 10 times larger than that without the sample, that is, S/N-ratio was about 10.This result was obtained for the sample of continuous alpha spectrum.For the sample of discrete spectrum S/N is expected to be much higher than this value if the source strength is same.Thus the alpha counting system now constructed can be applicable to low level alpha counting of various environmental materials if combined with the extracting technique of alpha emitting material.
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